There is a problem of obtaining a connection of a semiconductor part having a large pin number to a printed circuit board (substrate).
In general, the connection between the semiconductor part having a large pin number and the printed circuit board (substrate) is carried out by packaging. Particularly, a single chip type package mounting only one semiconductor part is typical.
Heretofore, one of such packages is called a PGA (Pin Grid Array) type. This package is constructed by connecting the semiconductor parts to a conductor circuit formed on the substrate using many conductor pins according to a given arrangement. Furthermore, a package called a TAB (Tape Automated Bonding) type is constructed by connecting a finger lead formed as a part of the conductor circuit on the substrate and connected to electronic circuit parts by thermal pressing and then potting it with a resin for sealing. Also, a packaged called a QFP (Quad Flat Package) type is constructed by connecting a lead frame to a semiconductor part through wire bonding and then subjecting it to transfer molding.
However, each of the conventional packages has defects. That is in the PGA package the pitch distance between the conductor pins is restricted, so that it is difficult to make the packaging density high. Furthermore, in the TAB type packages, it is necessary to use a special mounting machine in the heat pressing of finger leads to a semiconductor part, which is costly. Moreover, in the QFP type packages, it is difficult to form a fine pattern, so that the high density formation is not possible.
The inventors have particularly studied the QFP type package. As a result, when a semiconductor part, having a large number of terminals, is mounted onto the package, the substrate and particularly lead frame, having a fine pattern, should be used. However, the lead frame forming the substrate usually has a thickness of about 150 .mu.m for providing the strength. Therefore, the lead frame having such a thickness is difficult to be subjected to an etching, and particularly it is very difficult to form a lead frame having a fine pattern.
On the contrary, there have hitherto been proposed some techniques for improving the QFP type packages. For example, there is a package of such a type that the semiconductor part and lead frame are connected through a substrate provided with a fine conductor circuit. For instance, there are known
(a) a substrate having a conductor circuit and a lead frame which are electrically connected by wire bonding, and further the conductor circuit on the substrate and the semiconductor are connected by wire bonding and thereafter such an assembly is subjected to transfer molding to form a package; and PA1 (b) a substrate having a conductor circuit and a lead frame electrically connected by through-holes, and the conductor circuit and the semiconductor part are connected by wire bonding, and thereafter the assembly is subjected to transfer molding to form a package. PA1 (a) a step of shaping a base material into a lead frame; PA1 (b) a step of forming an adhesive layer on at least a part of the lead frame; PA1 (c) a step of forming a conductor circuit on the adhesive layer by an additive process; PA1 (d) a step of connecting the conductor circuit to leads of the lead frame through a conductor circuit for connection obtained by plating. PA1 (a) a step of shaping a base material into a lead frame; PA1 (b) a step of filling or coating an insulating material to at least one position in a gap between a lead and a die pad of the lead frame, a gap between the leads and a surface of the lead frame; PA1 (c) a step of forming an adhesive layer on at least a part of the lead frame; PA1 (d) a step of forming a plated conductor circuit on the adhesive layer by an additive process; PA1 (e) a step of connecting the plated conductor circuit to the leads of the lead frame by plating. PA1 (a) a step of forming an adhesive layer on at least a part of a substrate; PA1 (b) a step of forming a plated conductor circuit on the adhesive layer by an additive process; PA1 (c) a step of connecting the plated conductor circuit to a part of the base material by plating; PA1 (d) a step of subjecting the base material to etching to form a lead frame. PA1 (a) a step of forming an adhesive layer on at least a part of a base material; PA1 (b) a step of forming a plated conductor circuit on the adhesive layer by an additive process; PA1 (c) a step of connecting the plated conductor circuit to a part of the base material by plating; PA1 (d) a step of subjecting the base material to an etching to form a lead frame; PA1 (e) a step of filling or coating an insulating material to at least one position among a gap between a lead and a die pad of the lead frame, a gap between the leads and a surface of the lead frame. PA1 (a) a mixture of heat-resistant resin particles having an average particle size of 2-10 .mu.m and a fine powder of heat-resistant resin having an average particle size of not more than 2 .mu.m; PA1 (b) a pseudo-particle obtained by adhering a fine powder of heat-resistant resin having an average particle size of not more than 2 .mu.m to a surface of a heat-resistant resin particle having an average particle size of 2 to not more than 10 .mu.m; PA1 (c) an agglomerated particle having an average particle size of 2-10 .mu.m obtained by agglomerating a fine powder of heat-resistant resin having an average particle size of not more than 2 .mu.m with a heat-resistant resin hardly soluble in the oxidizing agent or acid. PA1 (a) the step of subjecting a base material to punching or the like to form a lead frame provided with a die pad; PA1 (b) the step of forming an adhesive layer on at least a part of the lead frame; PA1 (c) the step of forming a plated conductor circuit on the adhesive layer by an additive process; PA1 (d) the step of connecting the plated conductor circuit to leads of the lead frame by plating. PA1 (a) the step of subjecting a substrate to punching or the like to form a lead frame provided with a die pad; PA1 (b) the step of filling or coating an insulating material in gaps between the leads and the die pad of the lead frame or to at least one position of gaps between the leads and the surface of the lead frame; PA1 (c) the step of forming an adhesive layer on at least a part of the lead frame provided with the insulating material; PA1 (d) the step of forming a plated conductor circuit on the adhesive layer by an additive process; PA1 (e) the step of connecting the plated conductor circuit to leads of the lead frame by plating. PA1 (a) the step of forming an adhesive layer on at least a part of a base material (metal sheet); PA1 (b) the step of forming a plated conductor circuit on the adhesive layer by an additive process; PA1 (c) the step of connecting the plated conductor circuit to the substrate by plating; PA1 (d) the step of etching the substrate to form a lead frame provided with a die pad; or PA1 (a) the step of forming an adhesive layer on at least a part of a base material (metal sheet); PA1 (b) the step of forming a plated conductor circuit on the adhesive layer by an additive process; PA1 (c) the step of connecting the plated conductor circuit to the base material by plating; PA1 (d) the step of etching the substrate to form a lead frame provided with a die pad; PA1 (e) the step of filling or coating an insulating material in a gap between the lead and the die pad of the lead frame or to at least one position of gaps between the leads and the surface of the lead frame.
However, the former package in (a) has problems that the connection reliability is lacking because the connection of the lead frame to the circuit of the substrate is carried out by wire bonding. On the other hand, in the latter package (b), the connection of the lead frame to the circuit of the substrate is carried out by the through-holes, and high connection reliability is obtained, but there is a problem that the production process becomes very complicated. Furthermore, all of these improved packages are manufactured by combining the existing substrate with the existing lead frame, so that the cost becomes undesirably high.
An object of the invention is to establish a technique such that a semiconductor-mounting substrate used for mounting a semiconductor part, having many terminals onto a printed circuit board in a high density, can simply be manufactured with a high connection reliability and a low cost.